The present invention relates generally to a fluid machine, and more particularly to a hydraulic fluid machine. This term includes hydraulic pumps such as vane-type pumps and gear pumps.
In hydraulic fluid machines, such as vane-type pumps or gear pumps, it is desired to be able to axially center the rotor in the case of a vane-type pump, or the gears in the case of a gear-type pump. This is achieved in the prior art by providing at the opposite axial end faces of the rotor or gears respective compartments which are open to these end faces and which are in direct communication with the high pressure side of the pump or, in the case of gear pumps, even with the region where the gears interengage and thus produce pressure in the fluid. The concept behind this arrangement is the assumption that a centering of the gears or rotor in axial direction will be achieved, in that any axial shifting in one direction will cause in that compartment towards which the rotor or gear has shifted, an increase in pressure which will counteract the shifting and return the rotor or gear towards centered position. In actual fact it has, however, been observed that a sufficient pressure increase does not take place and that therefore the desired centering action is not reliably obtainable.